Most people when they talk about sleep apnea are referring to the most common type – obstructive sleep apnea (OSA). This type of sleep apnea is very common with some studies reporting a prevalence of 4% of the population and others reporting up to 20% of the general population.
Obstructive sleep apnea is caused by repeated full or partial obstructions of your upper airway while you sleep. During sleep the muscles throughout your body relax. This relaxation can lead to a collapse of the tongue or surrounding tissues against the back of the mouth blocking airflow.
To determine if you have obstructive sleep apnea, you need to have a sleep study. During the sleep study, we look to see the number of times per hour that you have the full or partial blockages of your upper airway – a number referred to the apnea-hypopnea index or AHI.
- < 5 times per hour is considered normal (and this rate is typically the goal for treatment)
- 5 to < 15 times per hour is mild sleep apnea
- 15 to < 30 times per hour is moderate sleep apnea
- 30 or more times per hour is severe sleep apnea
During these obstructions in your airway, the oxygen from the air can’t get in and the carbon dioxide from your lungs can’t get out. This leads to your oxygen periodically dropping throughout the night and sometimes your carbon dioxide levels can increase as well. Also, when you stop breathing, your body panics and does whatever it can to get you start breathing again. What often happens is that your brain makes you wake up (sometimes just for a few seconds so you don’t remember it) so that you start breathing again. These effects lead to a variety of negative health outcomes which I will discuss on a future podcast.
I want to point out that another type of sleep apnea exists, called central sleep apnea (CSA). Central sleep apnea is not caused by any physical narrowing of your airway but rather a signal (or a lack of a signal) from your brain that causes your body to take pauses in breathing.
Central sleep apnea is commonly caused by medications (most commonly opiates), medical conditions (such as congestive heart failure), or high altitudes. It can also be seen sometimes in people when they are put on PAP (positive airway pressure) treatment, which can resolve in some people over time. Sometimes central sleep apnea doesn’t have an identifiable cause.
Central sleep apnea is less common than obstructive sleep apnea. About 15% of people with sleep apnea have central sleep apnea. You can have both types of sleep apnea. Like obstructive sleep apnea, central sleep apnea is diagnosed by a sleep study.
Despite obstructive sleep apnea being very common, many people are undiagnosed. If you think you have sleep apnea, please talk with your doctor.
Remember to never drive or engage in activities requiring a high level of attention when drowsy.